1. Field of the Invention
The present invention relates to a battery device having a rechargeable battery such as a lithium-ion cell, and to a battery protection device for use in such a battery device.
2. Description of the Prior Art
A circuit of the type that produces an output signal by processing an input signal it receives is often so designed that, when the input signal once exceeds a predetermined level, the output of the circuit is locked in a fixed state and this locked state is maintained by a latch circuit. For example, in a case where the input signal is a monitoring signal that is used to monitor the condition of a system, such a circuit serves, when the system is in an abnormal condition, to prevent the aggravation of the condition by feeding its output signal back to the system.
Even when the system is brought back into a normal condition, the locked (i.e. latched) state persists. To cancel this locked state, it is necessary to expressly feed an unlatching signal to the latch circuit.
This requires the circuit, when it is formed as an IC (integrated circuit), to be provided with an extra terminal pin for receiving the unlatching signal, and thus to be provided with a larger number of terminal pins in total. This is disadvantageous for the miniaturization of the IC package and of the IC chip. The latched state can be canceled also by temporarily lowering the power source voltage supplied to the IC. However, this undesirably causes all the other circuits in the IC to be reset as well.